The present invention relates to a soft X-ray reduction projection exposure system, a soft X-ray reduction projection exposure method and a pattern formation method all using a soft X-ray beam as exposing light.
As the degree of integration of semiconductor integrated circuits is increased to further reduce the line width of circuits, lithography technique for forming a finer pattern is necessary.
Photolithography using KrF excimer laser (of a wavelength of 248 nm) is currently principally under development, and it is necessary to shorten the wavelength of exposing light in order to further increase the resolution.
It has been proved that a fine pattern with a width of 100 nm or less can be formed by photolithography using ArF excimer laser (of a wavelength of 193 nm) or F2 laser (of a wavelength of 157 nm) having a wavelength shorter than that of the KrF excimer laser.
Also, EUV lithography using a soft X-ray beam (of a wavelength of 13.4 nm) capable of realizing resolution of 30 nm has recently been developed.
An exposure system for the EUV lithography includes, as disclosed in Japanese Laid-Open Patent Publication No. 01-010625, a light source for generating a soft X-ray beam, a reflecting mask and a reduction projection optical system for transferring a pattern of the reflecting mask onto a wafer. The reduction projection optical system includes a combination of several non-spherical reflecting mirrors. Furthermore, since light does not transmit the air in the wavelength region of a soft X-ray beam (principally a 4 nm through 20 nm wavelength band), the inside of the exposure system should be evacuated.
A conventional exposure system for the EUV lithography has a problem of contamination of the reflecting mirrors and the reflecting mask with organic substances. The contamination is caused principally by a decomposed substance from a resist film and an organic substance adhered onto the inside wall of the exposure system. In particular, an organic substance floating within the exposure system is decomposed by the soft X-ray beam during the exposure and the thus decomposed substance is adhered onto the surface of the reflecting mirror, so that a carbon film may be deposited on the reflecting mirror.
When a carbon film is deposited on the reflecting mirror, the reflectance of the reflecting mirror is lowered. Therefore, the optical characteristic of the reduction projection optical system is harmfully affected and specifically, for example, aberration is caused. For example, if a carbon film with a thickness of 1 nm is deposited on a reflecting mirror made from a multi-layer film composed of a molybdenum film and a silicon film, the reflectance is lowered from 65% to 64%.
Furthermore, if the carbon film deposited on the reflecting mirror has an uneven thickness, large aberration is caused.
In consideration of the aforementioned conventional problems, an object of the invention is, in a soft X-ray reduction projection exposure system, a soft X-ray reduction projection exposure method and a pattern formation method using a soft X-ray beam as exposing light, preventing a carbon film from depositing on the surface of a reflecting mask, an illumination optical system for irradiating the reflecting mask with the soft X-ray beam or a reduction projection optical system for imaging a pattern of the reflecting mask.
In order to achieve the object, the first soft X-ray reduction projection exposure system of this invention comprises a light source for generating a soft X-ray beam of a wavelength of a 4 through 20 nm band; a reflecting mask on which a desired pattern is formed; an illumination optical system for irradiating the reflecting mask with the soft X-ray beam; a reduction projection optical system for imaging the pattern of the reflecting mask on a wafer; and controlling means for controlling a partial pressure of a gas of a carbon compound to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the first soft X-ray reduction projection exposure system, the controlling means controls the partial pressure of the gas of the carbon compound to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon is higher than a degree of absorbing carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less. As a result, the optical characteristic can be prevented from degrading due to contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the first soft X-ray reduction projection exposure system, the controlling means preferably reduces a pressure in at least one of the first region, the second region and the third region individually.
Thus, the partial pressure of the carbon compound gas can be controlled in a short period of time in any particular region where the partial pressure of the carbon compound gas is desired to be controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
In the first soft X-ray reduction projection exposure system, the controlling means preferably controls a total pressure to be 1.33xc3x9710xe2x88x924 Pa or less in any region where the partial pressure of the gas of the carbon compound is controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The second soft X-ray reduction projection exposure system of this invention comprises a light source for generating a soft X-ray beam of a wavelength of a 4 through 20 nm band; a reflecting mask on which a desired pattern is formed; an illumination optical system for irradiating the reflecting mask with the soft X-ray beam; a reduction projection optical system for imaging the pattern of the reflecting mask on a wafer; and capturing means for capturing a carbon compound generated in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the second soft X-ray reduction projection exposure system, the capturing means captures the carbon compound generated in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, the thickness of a carbon film deposited on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region can be suppressed. Accordingly, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the second soft X-ray reduction projection exposure system, the capturing means is preferably a filter cooled with liquid helium or liquid nitrogen.
Thus, the carbon compound generated in the first region, the second region or the third region can be definitely captured.
In the second soft X-ray reduction projection exposure system, the capturing means preferably captures the carbon compound in at least one of the first region, the second region and the third region individually.
Thus, the carbon compound can be definitely captured in any particular region where the carbon compound is desired to be captured among the first region, the second region and the third region.
In the first or second soft X-ray reduction projection exposure system, the carbon compound is preferably any of a hydrocarbon such as methane, ethane or propane, a straight-chain organic substance such as isopropyl alcohol or polymethyl methacrylate and a cyclic organic substance such as benzene or phthalate.
Thus, the organic substance that may contaminate the surface of the illumination optical system, the reflecting mask or the reduction projection optical system to degrade the optical characteristic can be definitely reduced.
The third soft X-ray reduction projection exposure system of this invention comprises a light source for generating a soft X-ray beam of a wavelength of a 4 through 20 nm band; a reflecting mask on which a desired pattern is formed; an illumination optical system for irradiating the reflecting mask with the soft X-ray beam; a reduction projection optical system for imaging the pattern of the reflecting mask on a wafer; and controlling means for controlling a partial pressure of an oxygen gas to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the third soft X-ray reduction projection exposure system, the controlling means controls the partial pressure of the oxygen gas to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to 0.1 nm or less.
Also, since the controlling means controls the partial pressure of the oxygen gas to be 1.33xc3x9710xe2x88x921 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the third soft X-ray reduction projection exposure system, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the third soft X-ray reduction projection exposure system, the controlling means preferably controls a total pressure to be 1.33xc3x9710xe2x88x921 Pa or less in any region where the partial pressure of the oxygen gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The fourth soft X-ray reduction projection exposure system of this invention comprises a light source for generating a soft X-ray beam of a wavelength of a 4 through 20 nm band; a reflecting mask on which a desired pattern is formed; an illumination optical system for irradiating the reflecting mask with the soft X-ray beam; a reduction projection optical system for imaging the pattern of the reflecting mask on a wafer; and controlling means for controlling a partial pressure of an ozone gas to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the fourth soft X-ray reduction projection exposure system, the controlling means controls the partial pressure of the ozone gas to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less.
Also, since the controlling means controls the partial pressure of the ozone gas to be 4.00xc3x9710xe2x88x922 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the fourth soft X-ray reduction projection exposure system, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the fourth soft X-ray reduction projection exposure system, the controlling means preferably controls a total pressure to be 4.00xc3x9710xe2x88x922 Pa or less in any region where the partial pressure of the ozone gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The first soft X-ray reduction projection exposure method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a wafer; and a controlling step of controlling a partial pressure of a gas of a carbon compound to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the first soft X-ray reduction projection exposure method, the partial pressure of the gas of the carbon compound is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon is higher than a degree of absorbing carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less. As a result, the optical characteristic can be prevented from degrading due to contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the first soft X-ray reduction projection exposure method, the controlling step preferably includes a sub-step of reducing a pressure in at least one of the first region, the second region and the third region individually.
Thus, the partial pressure of the carbon compound gas can be controlled in a short period of time in any particular region where the partial pressure of the carbon compound gas is desired to be controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
In the first soft X-ray reduction projection exposure method, the controlling step preferably includes a sub-step of controlling a total pressure to be 1.33xc3x9710xe2x88x924 Pa or less in any region where the partial pressure of the gas of the carbon compound is controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The second soft X-ray reduction projection exposure method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a wafer; and a capturing step of capturing a carbon compound generated in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the second soft X-ray reduction projection exposure method, the carbon compound generated in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed is captured in the capturing step. Therefore, the thickness of a carbon film deposited on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region can be suppressed. Accordingly, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the second soft X-ray reduction projection exposure method, the capturing step preferably includes a sub-step of capturing the carbon compound by using a filter cooled with liquid helium or liquid nitrogen.
Thus, the carbon compound generated in the first region, the second region or the third region can be definitely captured.
In the second soft X-ray reduction projection exposure method, the capturing step preferably includes a sub-step of capturing the carbon compound in at least one of the first region, the second region and the third region individually.
Thus, the carbon compound can be definitely captured in any particular region where the carbon compound is desired to be captured among the first region, the second region and the third region.
In the first or second soft X-ray reduction projection exposure method, the carbon compound is preferably any of a hydrocarbon such as methane, ethane or propane, a straight-chain organic substance such as isopropyl alcohol or polymethyl methacrylate, and a cyclic organic substance such as benzene or phthalate.
Thus, an organic substance that may contaminate the surface of the illumination optical system, the reflecting mask or the reduction projection optical system to degrade the optical characteristic can be definitely reduced.
The third soft X-ray reduction projection exposure method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a wafer; and a controlling step of controlling a partial pressure of an oxygen gas to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the third soft X-ray reduction projection exposure method, the partial pressure of the oxygen gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to 0.1 nm or less.
Also, since the partial pressure of the oxygen gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x921 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the third soft X-ray reduction projection exposure method, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the third soft X-ray reduction projection exposure method, the controlling step preferably includes a sub-step of controlling a total pressure to be 1.33xc3x9710xe2x88x921 Pa or less in any region where the partial pressure of the oxygen gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The fourth soft X-ray reduction projection exposure method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a wafer; and a controlling step of controlling a partial pressure of an ozone gas to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the fourth soft X-ray reduction projection exposure method, the partial pressure of the ozone gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less.
Also, since the partial pressure of the ozone gas is controlled, in the controlling step, to be 4.00xc3x9710xe2x88x922 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the fourth soft X-ray reduction projection exposure method, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the fourth X-ray reduction projection exposure method, the controlling step preferably includes a sub-step of controlling a total pressure to be 4.00xc3x9710xe2x88x922 Pa or less in any region where the partial pressure of the oxygen gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The first pattern formation method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a resist film; a step of forming a resist pattern by developing the resist film on which the pattern of the reflecting mask has been imaged; and a controlling step of controlling a partial pressure of a gas of a carbon compound to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the first pattern formation method, the partial pressure of the gas of the carbon compound is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x928 Pa or less in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon is higher than a degree of absorbing carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less. As a result, the optical characteristic can be prevented from degrading due to contamination, with an organic substance, on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the first pattern formation method, the controlling step preferably includes a sub-step of reducing a pressure in at least one of the first region, the second region and the third region individually.
Thus, the partial pressure of the carbon compound gas can be controlled in a short period of time in any particular region where the partial pressure of the carbon compound gas is desired to be controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
In the first pattern formation method, the controlling step preferably includes a sub-step of controlling a total pressure to be 1.33xc3x9710xe2x88x924 Pa or less in any region where the partial pressure of the gas of the carbon compound is controlled to be 1.33xc3x9710xe2x88x928 Pa or less among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The second pattern formation method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a resist film; a step of forming a resist pattern by developing the resist film on which the pattern of the reflecting mask has been imaged; and a capturing step of capturing a carbon compound generated in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the second pattern formation method, the carbon compound generated in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed is captured in the capturing step. Therefore, the thickness of a carbon film deposited on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region can be suppressed. Accordingly, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system.
In the second pattern formation method, the capturing step preferably includes a sub-step of capturing the carbon compound by using a filter cooled with liquid helium or liquid nitrogen.
Thus, the carbon compound generated in the first region, the second region or the third region can be definitely captured.
In the second pattern formation method, the capturing step preferably includes a sub-step of capturing the carbon compound in at least one of the first region, the second region and the third region individually.
Thus, the carbon compound can be definitely captured in any particular region where the carbon compound is desired to be captured among the first region, the second region and the third region.
In the first or second pattern formation method, the carbon compound is preferably any of a hydrocarbon such as methane, ethane or propane, a straight-chain organic substance such as isopropyl alcohol or polymethyl methacrylate, and a cyclic organic substance such as benzene or phthalate.
Thus, an organic substance that may contaminate the surface of the illumination optical system, the reflecting mask or the reduction projection optical system to degrade the optical characteristic can be definitely reduced.
The third pattern formation method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a resist film; a step of forming a resist pattern by developing the resist film on which the pattern of the reflecting mask has been imaged; and a controlling step of controlling a partial pressure of an oxygen gas to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the third pattern formation method, the partial pressure of the oxygen gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to 0.1 nm or less.
Also, since the partial pressure of the oxygen gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x921 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the third pattern formation method, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the third pattern formation method, the controlling step preferably includes a sub-step of controlling a total pressure to be 1.33xc3x9710xe2x88x921 Pa or less in any region where the partial pressure of the oxygen gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 1.33xc3x9710xe2x88x921 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.
The fourth pattern formation method of this invention comprises a step of introducing, by an illumination optical system, a soft X-ray beam of a wavelength of a 4 through 20 nm band to a reflecting mask on which a desired pattern is formed; a step of imaging, by a reduction projection optical system, the pattern of the reflecting mask on a resist film; a step of forming a resist pattern by developing the resist film on which the pattern of the reflecting mask has been imaged; and a controlling step of controlling a partial pressure of an ozone gas to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa in at least one of a first region where the illumination optical system is disposed, a second region where the reflecting mask is disposed and a third region where the reduction projection optical system is disposed.
In the fourth pattern formation method, the partial pressure of the ozone gas is controlled, in the controlling step, to be 1.33xc3x9710xe2x88x924 Pa or more in at least one of the first region where the illumination optical system is disposed, the second region where the reflecting mask is disposed and the third region where the reduction projection optical system is disposed. Therefore, a degree of releasing carbon through oxidation/decomposition is higher than a degree of adhering carbon on the surface of the illumination optical system disposed in the first region, the surface of the reflecting mask disposed in the second region or the surface of the reduction projection optical system disposed in the third region. Accordingly, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less.
Also, since the partial pressure of the ozone gas is controlled, in the controlling step, to be 4.00xc3x9710xe2x88x922 Pa or less, the transmittance loss per meter of the soft X-ray beam can be suppressed to 1% or less. Therefore, the proportion of the soft X-ray beam generated by the light source to reach the wafer cannot be lowered.
Accordingly, in the fourth pattern formation method, the optical characteristic can be prevented from degrading due to the contamination, with an organic substance, of the surface of the illumination optical system, the reflecting mask or the reduction projection optical system without increasing the transmittance loss of the soft X-ray beam.
In the fourth pattern formation method, the controlling step preferably includes a sub-step of controlling a total pressure to be 4.00xc3x9710xe2x88x922 Pa or less in any region where the partial pressure of the oxygen gas is controlled to be 1.33xc3x9710xe2x88x924 Pa through 4.00xc3x9710xe2x88x922 Pa among the first region, the second region and the third region.
Thus, the thickness of a carbon film deposited on the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be suppressed to approximately 0.1 nm or less, and in addition, the surface of the illumination optical system, the reflecting mask or the reduction projection optical system can be prevented from being contaminated with an inorganic substance.